The work of a student to solve a set of equations is shown:

Question

Equation A: y = 15 − 2z
Equation B: 3y = 3 − 4z

Step 1: −3(y) = −3(15 − 2z) [Equation A is multiplied by −3.]
3y = 3 − 4z [Equation B]
Step 2: −3y = 15 − 2z [Equation A in Step 1 is simplified.]
3y = 3 − 4z [Equation B]
Step 3: 0 = 18 − 6z [Equations in Step 2 are added.]
Step 4: 6z = 18
Step 5: z = 3
In which step did the student first make an error? (5 points)

Step 4

Step 3

Step 2

Step 1

Answer 1

The error occurred in Step 3. The student incorrectly added the equations in Step 2 instead of subtracting them.